M20 Grade 10.9 Torque Specification

Torque Values by Surface Condition

Stress area: 244.79 mm² · Proof load: 203,176 N · Clamp load (75%): 152,382 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	609.5	449.5	5394.5	6215.2
Oiled	0.15	457.1	337.1	4045.7	4661.1
Zinc Plated	0.18	548.6	404.6	4855.5	5594.2
Waxed	0.1	304.8	224.8	2697.7	3108.1
MoS₂	0.12	365.7	269.7	3236.7	3729.1
Galvanized	0.25	761.9	561.9	6743.4	7769.2

Stress area: 271.5 mm² · Proof load: 225,345 N · Clamp load (75%): 169,009 N

Surface Condition	K Factor	N·m	ft·lbs	in·lbs	kgf·cm
Plain/Dry	0.2	676.0	498.6	5983.1	6893.3
Oiled	0.15	507.0	373.9	4487.3	5170.0
Zinc Plated	0.18	608.4	448.7	5384.8	6204.0
Waxed	0.1	338.0	249.3	2991.6	3446.7
MoS₂	0.12	405.6	299.2	3589.9	4136.0
Galvanized	0.25	845.0	623.2	7478.9	8616.6

Formula: T = K × D × F

Step 1 — Clamp load: F = 0.75 × 830 MPa × 244.79 mm² = 152,382 N

Step 2 — Torque (dry): T = 0.20 × 0.0200 m × 152,382 N = 609.5 N·m

Proof stress per ISO 898-1:2013 Table 4. Stress area per ISO 898-1 Annex A. K-factor per VDI 2230.

Structural steel (equivalent to ASTM A490), heavy machinery, high-strength critical joints, pressure vessels

• Torque values are for standard hex bolts with ISO metric threads. Socket head cap screws may have different requirements.
• Lubrication reduces required torque significantly — using dry torque values on lubricated bolts risks exceeding yield strength.
• For critical or safety-related applications, always consult the manufacturer's specifications or applicable design standard (e.g., VDI 2230).
• Re-used bolts may have altered friction characteristics. Inspect threads before reuse.

SizeM20

Class10.9

Diameter20 mm

Pitch (coarse)2.5 mm

Tensile1040 MPa

Yield940 MPa

Proof830 MPa